1. Field of the Invention
The present invention relates to a sliding-vane rotary compressor for compressing a refrigeration medium or the like.
2. Description of the Prior Art
Sliding-vane rotary compressors, as disclosed for example in Japanese Utility Model Laid-open Publication No. 61-92778, include a compressor body composed of a cylinder block having an inside guide surface of an appropriate configuration, and front and rear side blocks disposed on opposite ends of the cylinder block, and a rotor rotatably disposed in the compressor body and carrying thereon a plurality of radially movable sliding vanes held in contact with the guide surface of the cylinder block.
The rotor is concentrically and fixedly mounted on a drive shaft which is rotatably supported on the front and rear side blocks via a pair of bearings, with an appropriate clearance between each respective side block and the rotor for smooth rotation of the rotor. The vanes, rotor, cylinder block and front and rear side blocks jointly define therebetween a plurality of compression chambers in which a refrigeration medium is compressed.
The drive shaft has a front side end operatively connected with an electromagnetic clutch for receiving a rotational power or torque via the electromagnetic clutch. When the electromagnetic clutch is energized, a clutch plate is pulled or attracted to the rotor so that a drive force is transmitted to the drive shaft, thereby rotating the rotor of the rotary compressor. With rotation of the rotor, the vanes slide along the guide surface of the cylinder block to cause the compression chambers to be subsequently increased and decreased in volume with each revolution of the rotor, whereby the refrigeration medium drawn into the compression chamber is compressed, then discharged therefrom through discharge holes by forcibly opening reed valves associated with the respective discharge holes.
The conventional sliding-vane rotary compressors of the foregoing construction have a problem that an unpleasant noise is produced while the compressor is operating. More specifically, in a sliding-vane rotary compressor having a total of five sliding vanes, the torque fluctuation occurs ten times per a single revolution of the rotor while the load fluctuation occurs five times per a single revolution of the rotor. Such torque and load fluctuations produce a higher harmonic resonance of the rotor which in turn brings about resonant vibration of other components. Thus, an unpleasant operation noise is produced from the rotary compressor.
The unpleasant noise is caused by the presence of a clearance which is provided between the front side block and the rotor and also between the rotor and the rear side block for enabling a smooth rotation of the rotor. With the clearance thus provided, the rotor is caused to oscillate in the axial direction when subjected to periodical forcers produced in response to the fluctuation of load on the rotor.